The present invention relates to breakaway protection for a trailer which is adapted to be hitched to a towing vehicle such as an automobile or truck. More particularly, the invention is adapted for use with a trailer having wheels with brakes which are engaged when associated electrical coils are energized from the towing vehicle during normal towing operations.
The trailer can sometimes break loose from the towing vehicle and run wildly down the road. To prevent this, a breakaway switch is provided between the towing vehicle and the trailer. If the trailer breaks loose, the breakaway switch is automatically rendered conductive and energizes the brake coils by means of an auxiliary battery which is carried on the trailer. But if the auxiliary battery is weak or dead and does not have sufficient storage capacity to adequately energize the coils, the brakes will not be safely applied during breakaway and the trailer thus can run wildly.
The aforementioned Myers application discloses a voltage indicator with which the driver may test the auxiliary battery to determine not only whether the battery has sufficient voltage to initially energize the brake coils but also whether the battery has adequate storage capacity to hold such voltage and keep the coils safely energized for a sustained period during breakaway. If the battery is "good," the voltage indicator provides the driver with a visual signal informing the driver that it is safe to tow the trailer. But the voltage indicator also can provide a "safe" signal when in fact the system is not safe by reason of, for example, an interruption of the excitation circuit to the brake coils or the loss of one or more coils from the circuit.